Fourier transform infrared (FTIR) spectroscopy will be utilized as a probe for specific conformational changes in two purified complexes of the respiratory chain isolated from beef heart mitochondria. Shifts in the infrared absorption band for protein sulfhydryl groups, attributed to conformational changes associated with respiration, will be studied in the cytochromes b-c7 complex (Complex III) and the cytochrome oxidase complex (Complex IV). FTIR spectroscopy also will be used to study possible spectral perturbations of carbon monoxide bound to cytochrome oxidase as a function of respiratory state. These studies hopefully will provide information on the role of conformational changes in the respiratory and energy conserving function of the respiratory assembly as well as developing techniques for the application of FTIR spectroscopy to other biological and medical investigations.